Question

Distinguish between positive and negative work. When you lift an object, 2 objects act on it. Identify these forces. Which one of the two does, [a}. positive work ? {b}. negative work ? Justify your answer

Answer 1

when we lift an object 2 forces acts on it these are:
(I) muscular force
and
(II) gravitational force
a. positive work is done by the muscular force because the displacement is in the direction of the muscular force .
b. negative work is down by the gravitational force because displacement is in the opposite direction to which the gravitational force is acting ... 
i hope it helps....

Answer 2

muscular and gravitational force are accting